1. Field of Invention
The present invention relates to wireless communications and, more particularly, to seamlessly handing off a call from one wireless network that uses a particular transmission method to a different wireless network that uses a different transmission method.
2. Description of Related Art
Devices are available that have both cellular capability and capability to perform under the standard of the Institute of Electrical and Electronics Engineering (IEEE) known as the IEEE 802.1x standard. Such devices include, for example, laptop computers and personal digital assistants (PDAs). Cellular networks use transmission methods that are different from the transmission methods used in 802.1x networks. The transmission methods used by cellular networks are governed by standards such as WCDMA, GPRS, 1XRT, 3XRT and EDGE, for example. The transmission methods used by 802.1x networks are governed by the applicable IEEE 802.1x standard. The term 802.1x, as that term is used herein, means all of the IEEE standards that have the prefix 802.1, including, but not limited to, 802.11, 802.11a, 802.11b, 802.11c, 802.11d, 802.11e, 802.11f, 802.11g, 802.11h, 802.11i, etc. 802.1x networks use the Transport Control Protocol/Internet Protocol (TCP/IP) to enable wireless devices with 802.1x capabilities to wirelessly connect to access points of wired and wireless local area networks (LANs). Voice, data, video and audio are transmitted over 802.1x networks in TCP/IP packets.
An 802.1x network access point has a limited distance over which it can communicate with a wireless device. When the 802.1x device moves out of range of the access point, the call is dropped. The call may be communicating voice, data, video or audio at the time it is dropped. There may be times when an 802.1x-capable device, such as a PDA, for example, is out of range of a 802.1x access point, but within range of a cellular base station transmitter. However, even though devices exist that have both cellular and 802.1x capabilities, such devices do not have the capability to seamlessly switch from communicating over an 802.1x network to communicating over a cellular network, or vice versa. Therefore, the user is faced with having to manually establish communication with the cellular network after the call has been dropped. Of course, resuming a call in this manner may result in information being lost, regardless of whether voice, data, video or audio is being communicated. An analogous situation occurs when a device moves out of range of a cellular network and within range of an access point of an 802.1x network.
It would be desirable to provide the capability of performing a seamless handoff of a call from an 802.1x network to a cellular network, and vice versa.